A U.S. Defense official told CNN this morning that the missile that hit Malaysia Airlines flight MH17 yesterday was most likely fired by pro-Russian separatists inside eastern Ukraine. This information comes from "a preliminary classified U.S. intelligence analysis."

Last night, Hillary Clinton told Charlie Rose that there was "growing awareness" that the attack, which killed 283 passengers and 15 crew, "probably had to be [carried out by] Russian insurgents." C.J. Chivers at The New York Times explained earlier how the separatists could have accessed the kind of missile — an SA-11, or "Buk" — that U.S. officials suspect was used in the attack:

Ukrainian and American officials have accused Russia of providing the separatists with many sophisticated and powerful weapons, and the rebels have also captured many Ukrainian weapons, meaning they could have obtained SA-11s from either source.

A social media post attributed to Igor Strelkov, the shadowy pro-Russian commander, showed him claiming to have captured Buk missiles. That claim has not been verified independently, and the rebels have been given to boasts.

Since the attack, Ukraine and the separatists have blamed each other. Russian President Vladimir Putin blamed Ukraine in his statement: "Certainly, the state over whose territory this happened bears responsibility for this terrible tragedy. This tragedy would not have happened if there was peace in this land, they would not have been renewed war-like actions in the southeast of Ukraine."

Malaysia Airlines flight MH17, which was carrying 298 passengers and crew, was shot down today…
Read more Read more

The separatists have offered a brief cease-fire so that investigators and crew can access the crash site. There's been some speculation that evidence may have been tampered with at the site—the White House released a statement last night saying "it is vital that no evidence be tampered with in any way and that all potential evidence and remains at the crash site are undisturbed."

Today, rebel leaders made conflicting statements about whether or not they had found black boxes. Rebel leader Aleksander Borodai claimed no black boxes had been found, but before that, an aide to rebel military leader Igor Girkin said eight of 12 recording devices were recovered. For what it's worth, planes typically only have two black boxes.

Update, 11:41 am: The U.S. says it can't rule out Russian help to separatists to down the plane. U.S. Ambassador to the U.N. Samantha Power said today, "Because of the technical complexity of the SA-11 it is unlikely that the separatists could effectively operate the system without assistance from knowledgeable personnel, thus we cannot rule out technical assistance from Russian personnel in operating the system."